There are a number of significant challenges facing public carriers in telecommunications markets, including a rapidly growing demand for Internet data access over the public switched telephone network (PSTN). The demand for Internet access has been so great that there has been a considerable increase in call holding times on calls to Internet service providers and delays in making connections to the PSTN. In addition, even when connections are made to the Internet, the bandwidth demand imposed by the increasing number of users has strained conventional narrowband network systems and has deteriorated existing service on the PSTN, particularly in North America.
Deregulation and growth in the use of wireless systems, particularly cellular telephones and portable data communications devices, has also strained existing network systems and has created a demand for trunking growth. As more users connect into analog and digital cellular systems, telecommunications carriers will have to expand existing network switching systems and increase trunking capacity between switching systems.
A problem with existing networks is that the interexchange trunks in those networks serve as traffic capacity choke points in the system. That is, the trunks limit the amount of traffic that can be passed between access tandems in the PSTN. In order to handle a large call volume, or the increased call volume due to the sudden growth of the usage of the network for data services, the trunks need to be provisioned with a capacity to handle high call volumes. If the trunk capacity of the access tandems is exceeded, then access tandems also have to be added to the network. Not only is the provisioning of access tandems and interexchange trunking very expensive, such facilities are generally not adapted to support other services during off-peak hours.
The above-mentioned problems typically cause switch port capacity exhaustion in the tandem layer of a voice network. This problem has been addressed by deploying solutions to redirect the traffic to a data network at an access interface or an end office. One such solution is proposed in U.S. Pat. No. 5,483,527 to Doshi et al., issued Jan. 9, 1996. One of the principles behind this patent is to accumulate voice signals from synchronous transfer mode switches (STMs) and form asynchronous transfer mode (ATM) cells from the signals. After a pre-determined number of signals are received, the cell is transferred over an ATM switching system, and the data is converted back to synchronous transfer mode voice signals.
A drawback of the Doshi et al. system is that it essentially imposes a synchronous transfer mode architecture on the ATM network. Telephone calls are transferred through the ATM network using permanent virtual circuits and each of the asynchronous transfer mode switches in the network is provided with a signal processor and call processor that receive common channel signaling messages and transfer those messages on to a next switch in the ATM call path or the destination switch in the telephone network, as appropriate. Since every single ATM switch requires those signal and call processors, this configuration is expensive to implement. It also leads to an inefficient usage of available bandwidth on the network. Therefore, a need exists in the telecommunications markets for a system which can improve bearer traffic capacity using ATM facilities, while permitting efficient usage of available bandwidth on the ATM network. A need also exists for a system which can increase bearer traffic capacity using an ATM network control system that readily integrates with various types of TDM switches that exist in the PSTN network. An additional need exists for a subnetwork which can absorb additional growth in call volumes so as to prevent the need for provisioning trunks with a capacity to handle high call volumes. A further need exists for a subnetwork which eliminates the requirement to provision high capacity trunking connection in existing synchronous transfer mode (STM) networks.